Get value from Embedded Document Mongo Java

Question

I have the following document in mongo:

>  {    "_id": ObjectId("569afce4b932c542500143ec"),    
>    "date": "2016-1-17T2:31:0Z",    
>    "day": NumberInt(17),    
>    "model1": {
>      "date": "2016-01-17T02:31+0000",
>      "MondayModel": {
>        "gtxdotdot": {
>          "xdotdot": 0,
>          "xdot": 0
>       },
>        "lsxdotdot": {
>          "xdotdot": 0,
>          "xdot": 0
>       },
>        "gtxdot": {
>          "xdotdot": 0,
>          "xdot": 0
>       },
>        "lsxdot": {
>          "xdotdot": 0,
>          "xdot": 0
>       },
>        "modeldotdot": {
>          "mean": 0,
>          "sdvar": 0
>       },
>        "modeldot": {
>          "mean": 0,
>          "sdvar": 0
>       }
>     } 
>     }

I wish to both find this document and extract only the values of model1.MondayModel.gtxdotdot.xdotdot/xdot/mean/sdvar ...

My current code does so with the following:

MongoCursor<Document>  back = collection.find(and(eq("topic",topic),eq("sp",sp))).limit(1).iterator();
if (back.hasNext())
{
    Document doc = back.next();
    Document tmpddc1 = (Document)doc.get("model1");
    Document tmpddc2 = (Document)tmpddc1.get("MondayModel");

    Document tmpddc3 = (Document)tmpddc2.get("gtxdotdot");
    gtxdotdotXdotdot = tmpddc3.getDouble("xdotdot");
    gtxdotdotXdot    = tmpddc3.getDouble("xdot");

             tmpddc3 = (Document)tmpddc2.get("lsxdotdot");
    lsxdotdotXdotdot = tmpddc3.getDouble("xdotdot");
    lsxdotdotXdot    = tmpddc3.getDouble("xdot");

             tmpddc3 = (Document)tmpddc2.get("gtxdot");
    gtxdotXdotdot = tmpddc3.getDouble("xdotdot");
    gtxdotXdot    = tmpddc3.getDouble("xdot");            

             tmpddc3 = (Document)tmpddc2.get("lsxdot");
    lsxdotXdotdot = tmpddc3.getDouble("xdotdot");
    lsxdotXdot    = tmpddc3.getDouble("xdot");  


             tmpddc3 = (Document)tmpddc2.get("modeldotdot");
    modeldotdotXmean = tmpddc3.getDouble("mean");
    modeldotdotXsdvar    = tmpddc3.getDouble("sdvar");             

             tmpddc3 = (Document)tmpddc2.get("modeldot");
    modeldotXmean = tmpddc3.getDouble("mean");
    modeldotXsdvar    = tmpddc3.getDouble("sdvar");                         

}

Instead of running thought he document (as above) is there a way to get the values using the dot notation [model1.MondayModel.gtxdotdot.xdotdot] ? Something such as:

double value =  doc.getDouble("model1.MondayModel.gtxdotdot.xdotdot");

Answer 1

You can do it one of three ways.

You can use aggregation framework to project the value of embedded field using dot notation.

Using Aggregation

 import static com.mongodb.client.model.Aggregates.*;
 import static com.mongodb.client.model.Filters.eq;
 import static com.mongodb.client.model.Projections.computed;
 import static java.util.Arrays.*;
 import static com.mongodb.client.model.Projections.include;

 MongoClient mc = new MongoClient();
 MongoDatabase db = mc.getDatabase("test");
 MongoCollection<Document> collection = db.getCollection("collection");
 Document document = 
     collection.aggregate(asList(
        match(eq("day",17)),
        project(computed("val", "$model1.MondayModel.gtxdotdot.xdotdot")))).
     first();
 Double embeddedField = document.getDouble("val");

Using Distinct

 Double embeddedField = collection.distinct("model1.MondayModel.gtxdotdot.xdotdot", eq("day",17), Double.class).first();

Using Find

 Document document = collection.find(eq("day",17)).projection(include("model1.MondayModel.gtxdotdot.xdotdot")).first();
 Double embeddedField = document.get("model1", Document.class).get("MondayModel", Document.class).get("gtxdotdot", Document.class).getDouble("xdotdot")